Method and system for providing adjustable compression force on a tube in a peristaltic pump

ABSTRACT

A cassette for use in a peristaltic pump is provided. The cassette includes a cassette frame, a cam, a cam position selector switch, and a biasing member. The cassette frame mounts to the peristaltic pump. The biasing member mounts to the cam and to the cassette frame and operably couples with the cam position selector switch. Moving the cam position selector switch in a first direction releases the cam position selector switch from the cassette frame. Moving the cam position selector switch in a second direction after releasing the cam position selector switch from the cassette frame adjusts a position of the cam relative to the cassette frame. The second direction is approximately perpendicular to the first direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of International Application No. PCT/FR2005/001524 filed on Jun. 17, 2005, the entire contents of which is hereby incorporated by reference; which claims the benefit of French Patent Application No. 04/06764 that was filed Jun. 22, 2004, the entire contents of which is hereby incorporated by reference.

FIELD

The field of the disclosure relates generally to peristaltic pumps. More specifically, the disclosure relates to cassettes that provide an adjustable compression force on a tube used in a peristaltic pump.

BACKGROUND

Peristaltic pumps have been known for many years, and are commonly used for medical and research purposes. Peristaltic pumps move a liquid through a tube without any part of the pump ever touching the liquid. As a result, it is possible to pump liquids, such as blood, which are sensitive to external contamination. Typically, a pump comprises rotating rollers that compress a part of the flexible tube as they move, which propels the liquid through the tube.

For example, such a pump is described in document EP 339 857. The flexible tube must withstand the compressive force while remaining absolutely leak proof. The pump in the aforesaid document includes removable cassettes that each include a tube and a sliding movable cam that pushes the tube against the rollers to ensure good contact between tube and rollers. To maintain the tube's lifetime, the pump includes means to modulate the compressive force exerted by the cam on the tube. These means include two wedges which move inside the cassette in order to adjust the position of the cam relative to the tube. Each wedge is connected with the threaded part of a rod whose rotation can be externally controlled with a knob. However, this configuration requires a relatively long time to adjust the cam position when it is necessary to change the compressive force over a large range. Thus, what is needed is a method and a system for providing a rapid adjustment of the cam position relative to a tube in a peristaltic pump.

SUMMARY

A method and a system for adjusting a position of a cam in a peristaltic pump is provided in an exemplary embodiment. The position of the cam is easily and quickly moved even over a large range. By adjusting the position of the cam, the compression force on the tube placed in the peristaltic pump is modified to accommodate different size tubes and different types of fluid flowing through the tube by the action of the pump.

In an exemplary embodiment, a cassette for use in a peristaltic pump is provided. The cassette includes, but is not limited to, a cassette frame a cam, a cam position selector switch, and a biasing member. The cassette frame mounts to the peristaltic pump. The biasing member mounts to the cam and to the cassette frame and operably couples with the cam position selector switch so that movement of the cam position selector switch adjusts a position of the cam relative to the cassette frame.

In an exemplary embodiment, a peristaltic pump is provided. The peristaltic pump includes, but is not limited to, a pump frame, a plurality of rollers configured to mount to the pump frame, an actuator operably coupled to move the plurality of rollers, and a cassette. The cassette includes, but is not limited to, a cassette frame, a cam, a cam position selector switch, and a biasing member. The cassette frame mounts to the pump frame and receives a tube. The cam is positioned to compress the received tube against the plurality of rollers. The biasing member mounts to the cam and to the cassette frame and operably couples with the cam position selector switch so that movement of the cam position selector switch adjusts a position of the cam relative to the cassette frame.

In another exemplary embodiment, a method of adjusting a position of a cam in a peristaltic pump is provided. A cassette is mounted to the peristaltic pump. The cassette includes, but is not limited to, a cassette frame, a cam, a cam position selector switch, and a biasing member. The biasing member mounts to the cam and to the cassette frame and operably couples with the cam position selector switch. Moving the cam position selector switch in a first direction releases the cam position selector switch from the cassette frame. Moving the cam position selector switch in a second direction after releasing the cam position selector switch from the cassette frame adjusts a position of the cam relative to the cassette frame. The second direction is approximately perpendicular to the first direction.

Other principal features and advantages of the invention will become apparent to those skilled in the art upon review of the following drawings, the detailed description, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like numerals denote like elements.

FIG. 1 is a perspective view of a peristaltic pump head with a cassette in a position to be installed onto the pump in accordance with an exemplary embodiment.

FIG. 2 is a perspective view of the peristaltic pump head of FIG. 1 with the cassette installed on the pump in accordance with an exemplary embodiment.

FIG. 3 is a front cross sectional view of the pump head of FIG. 2 with the cassette in accordance with an exemplary embodiment.

FIG. 4 is a front view of the cassette of FIG. 1 with some hidden parts illustrated with dashed lines in accordance with an exemplary embodiment.

FIG. 5 is a front perspective view of the cassette of FIG. 1 in accordance with an exemplary embodiment.

DETAILED DESCRIPTION

With reference to FIG. 1, a peristaltic pump head 2 of a peristaltic pump is shown in accordance with an exemplary embodiment. The peristaltic pump may include peristaltic pump head 2 and an actuator. Peristaltic pump head 2 may include a crankcase 4, a frame 5, a plurality of rollers 8, and a cassette 18. Frame 5 may include a center support 10, a front wall 12, a back wall 14, and two braces 20. Crankcase 4 mounts to front wall 12 and includes an axis of symmetry 6. As used in this disclosure, the term “mount” includes join, unite, connect, associate, insert, hang, hold, affix, attach, fasten, bind, paste, secure, bolt, screw, rivet, solder, weld, and other like terms.

In the exemplary embodiment of FIG. 1, the plurality of rollers 8 includes eight rollers symmetrically arranged around the axis of symmetry 6. The rollers are mounted in a rotating fashion on central support 10. In the exemplary embodiment of FIG. 1, each roller of the plurality of rollers 8 has a spherical shape and rotates about an axis parallel to the axis of symmetry 6. Central support 10 rotates around the axis of symmetry 6.

The actuator is operably coupled to rotate the plurality of rollers 8. For example, the actuator may include a rotor connected to the plurality of rollers through a shaft 11 as known to those skilled in the art. The actuator may be any device as known to those skilled in the art for causing rotation of the plurality of rollers. Exemplary actuators include an electric motor, a servo, stepper, or piezo motor,a pneumatic actuator, a gas motor, etc.

Front wall 12 and back wall 14 define between them a housing 16 sized to accommodate one or more cassettes 18. Front wall 12 and back wall 14 are linked together by the two braces 20 which extend parallel to the axis of symmetry 6, and act as a support and locking mechanism for cassette 18. With reference to FIG. 1, cassette 18 is shown released from the two braces 20. With reference to FIG. 2, cassette 18 is shown mounted to the two braces 20 for use with the peristaltic pump. Cassette 18 may or may not be removable from the peristaltic pump in alternative embodiments. A plurality of cassettes 18 can be held in housing 16 as indicated in FIG. 2, side by side, parallel to one another, and/or in contact with each other. When mounted to frame 5, cassette 18 extends parallel to front wall 12 and back wall 14 in a plane, which is perpendicular to the axis of symmetry 6.

With reference to FIG. 5, a front perspective view of cassette 18 is shown in accordance with an exemplary embodiment. Each cassette is basically flat. Cassette 18 includes a cassette frame 22. In the exemplary embodiment of FIG. 5, cassette frame 22 has essentially an inverted U shape formed by a front wall 36 and a back wall (not shown) with a frame edge 26 extending between front wall 36 and the back wall. A cavity 30 (shown with reference to FIG. 4) is formed between front wall 36 and the back wall. The inverted U shape of cassette frame 22 formed by front wall 36 and the back wall includes legs 28 which extend from a top brace 29.

Cassette frame 22 may include notches 25 located near the lower ends of legs 28 opposite top brace 29. Cassette 18 mounts and locks onto peristaltic pump head 2 at the ends of legs 28 adjacent notches 25. For example, a hook 31 extends from at least one of the legs 28 and mounts to at least one of the braces 20 of frame 5. A peripheral edge 61 in frame edge 26 defines a portion of a slot 53 within which a knob 60 is configured to move.

Cassette 18 includes a cam 32 accommodated in cavity 30. Cam 32 has an essentially flat rectangular shape with a saddle-shaped hollow formed by a lower edge 34 designed to face the plurality of rollers 8. Front wall 36 and the back wall partially cover each side of cam 32.

With reference to FIG. 3, a front cross sectional view of cassette 18 mounted to frame 5 is shown in accordance with an exemplary embodiment. A flexible tube 24 is mounted to cassette frame 22 in a removable manner. In particular, flexible tube 24 is held in notches 25. Tube 24 rests against lower edge 34 of cam 32. The part of tube 24 resting against lower edge 34 extends between the parts of tube 24 housed in notches 25. Cassette 18 includes a biasing member 38. In an exemplary embodiment, biasing member 38 is a blade spring.

With reference to FIG. 4, a front view of cassette 18 with some hidden parts illustrated with dashed lines is shown in accordance with an exemplary embodiment. Cassette 18 includes a cam position selector switch 56. In the exemplary embodiment of FIG. 4, cam position selector switch 56 includes a first edge 55, a second edge 62, and knob 60. First edge 55 includes a plurality of ridges. The plurality of ridges may have a scalloped or serrated shape. Second edge 62 is generally opposite first edge 55 and is inclined relative to first edge 55. Knob 60 extends from first edge 55 in a direction opposite second edge 62.

Cassette frame 22 may include a peripheral wall 63 which extends from peripheral edge 61 and defines slot 53 within which knob 60 is configured to move. Cassette frame 22 further may include an interior surface 57, which extends from peripheral wall 63 in a generally perpendicular direction to peripheral wall 63. Interior surface 57 defines a surface of a hollow 54 formed within top brace 29. Cam position selector switch 56 is received within slot 53 and hollow 54 of cassette frame 22.

In the exemplary embodiment of FIG. 4, interior surface 57 includes a second plurality of ridges. The plurality of ridges of first edge 55 of cam position selector switch 56 are configured to abut the second plurality of ridges of interior surface 57 of cassette frame 22. As a result, the plurality of ridges of first edge 55 of cam position selector switch 56 and the second plurality of ridges of interior surface 57 form a series of cogs which engage with each other.

Cassette frame 22 further may include a push button 50 mounted for movement in a first direction within hollow 54. Push button 50 may have the general shape of a rectangular parallelepiped. The underside of push button 50 may be in contact with an upper side of the center of biasing member 38. The underside of push button 50 may be mounted to the upper side of the center of biasing member 38. Push button 50 slides within two channels 52 located within top brace 29. The channels extend generally perpendicular to the elongate direction of top brace 29 so that push button 50 may move vertically.

A center of biasing member 38 extends near a central part of top brace 29. In the exemplary embodiment of FIG. 4, biasing member 38 includes two tips 27. Hooks 40 may extend from an upper edge 41 of cam 32 generally opposite lower edge 34. Cam 32 mounts to biasing member 38 near the tips 27, for example, using the hooks 40. The tips 27 are visible through openings 42 located in front wall 36 and the back wall of cassette frame 22. As a result, cam position selector switch 56 rests against push button 50 which contacts biasing member 38, which acts downwards on cam 32, which in turn acts downwards on tube 24 and towards the plurality of rollers 8. Cam position selector switch 56 thereby provides a control of the cam's compression force on tube 24.

Moving knob 60 of cam position selector switch 56 in the first direction, which defines the direction of movement of push button 50, releases first edge 55 of cam position selector switch 56 from the second plurality of ridges of interior surface 57 of cassette frame 22. In the exemplary embodiment of FIG. 4, the first direction is towards cam 32. Moving knob 60 of cam position selector switch 56 in a second direction after releasing cam position selector switch 56 from cassette frame 22 adjusts a position of cam 32 relative to cassette frame 22 due to the inclined surface of second edge 62. Cam 32 moves toward or away from the plurality of rollers 8 depending on the direction of the slope of second edge 62 and the direction of movement, by the user, of knob 60. The second direction is approximately perpendicular to the first direction and in the elongate direction of top brace 29. Releasing cam position selector switch 56 causes the plurality of ridges of first edge 55 to again abut the second plurality of ridges of interior surface 57 though possibly with a different alignment of ridges. Releasing cam position selector switch 56 holds cam position selector switch 56 in position through the interaction of the plurality of ridges of first edge 55 which cooperate with the second plurality of ridges of interior surface 57 and through the compression force exerted by biasing member 38.

The upper side of cassette 18 can be marked to indicate various positions of cam position selector switch 56 corresponding to a predetermined compression strength. A scale can therefore be used to identify and to control the compression strength For example, the scale may be based on the diameter of tube 24 used. By placing cam position selector switch 56 on top of cassette 18, it is easy to control, to read, and to repeat the setting of the desired compression force. Use of push button 50, an intermediate part, helps prevent transmission of lateral forces between cam position selector switch 56 and cam 32. Cassette 18 may not include a biasing member 38 such that push button 50 may directly contact cam 32 to provide the position adjustment.

The method and system described provide control of the compression force on tube 24. For example, depending on the diameter of tube 24, the compression force can be optimized for the desired flow rate and pressure based on certain characteristics of the fluid flowing through tube 24. Additionally, an improved efficiency and a longer tube lifetime can be achieved. Moving cam position selector switch 56 changes the compression of biasing member 38, and therefore, by interaction, the strength of the compression force on tube 24 via cam 32. The complementary shape of the plurality of ridges ensures that cam position selector switch 56 remains in its resting position, while permitting modulation of the compression force simply and quickly.

The foregoing description of exemplary embodiments of the invention have been presented for purposes of illustration and of description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and as practical applications of the invention to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents. 

1. A cassette for use in a peristaltic pump, the cassette comprising: a cassette frame configured to mount to a peristaltic pump and to receive a tube; a cam; a cam position selector switch; and a biasing member mounted to the cam and to the cassette frame and operably coupled with the cam position selector switch so that movement of the cam position selector switch adjusts a position of the cam relative to the cassette frame.
 2. The cassette of claim 1, wherein the cam position selector switch comprises: a first edge, the first edge including a plurality of ridges; a second edge, the second edge generally opposite the first edge, the second edge inclined relative to the first edge; and a knob extending from the first edge.
 3. The cassette of claim 2, wherein the cassette frame comprises an exterior surface and a peripheral wall, wherein the peripheral wall includes a peripheral edge in the exterior surface, the peripheral wall defining a slot within which the knob is configured to move.
 4. The cassette of claim 3, wherein the cassette frame includes an interior surface, the interior surface extending from the peripheral wall and including a second plurality of ridges, wherein the plurality of ridges are configured to abut the second plurality of ridges.
 5. The cassette of claim 4, wherein the cassette frame includes a push button mounted for movement in a first direction, wherein the second edge contacts the push button to cause the movement in the first direction.
 6. The cassette of claim 5, wherein the biasing member mounts to the push button.
 7. The cassette of claim 6, wherein the biasing member is a blade spring mounted to the push button near a center of the blade spring.
 8. The cassette of claim 7, wherein the blade spring includes a first tip and a second tip opposite the first tip, and further wherein the cam mounts to the blade spring near the first tip and near the second tip.
 9. A peristaltic pump, the peristaltic pump comprising: a pump frame; a plurality of rollers configured to mount to the pump frame; an actuator operably coupled to move the plurality of rollers; a cassette, the cassette comprising a cassette frame configured to mount to the pump frame and to receive a tube; a cam positioned to compress the received tube against the plurality of rollers; a cam position selector switch; and a biasing member mounted to the cam and to the cassette frame and operably coupled with the cam position selector switch so that movement of the cam position selector switch adjusts a position of the cam relative to the cassette frame.
 10. The cassette of claim 9, wherein the cam position selector switch comprises: a first edge, the first edge including a plurality of ridges; a second edge, the second edge generally opposite the first edge, the second edge inclined relative to the first edge; and a knob extending from the first edge.
 11. The cassette of claim 10, wherein the cassette frame comprises an exterior surface and a peripheral wall wherein the peripheral wall includes a peripheral edge in the exterior surface, the peripheral wall defining a slot within which the knob is configured to move.
 12. The cassette of claim 11, wherein the cassette frame includes an interior surface, the interior surface extending from the peripheral wall and including a second plurality of ridges, wherein the plurality of ridges are configured to abut the second plurality of ridges.
 13. The cassette of claim 12, wherein the cassette frame includes a push button mounted for movement in a first direction, wherein the second edge contacts the push button to cause the movement in the first direction.
 14. The cassette of claim 13, wherein the biasing member mounts to the push button.
 15. The cassette of claim 14, wherein the biasing member is a blade spring mounted to the push button near a center of the blade spring.
 16. The cassette of claim 15, wherein the blade spring includes a first tip and a second tip opposite the first tip, and further wherein the cam mounts to the blade spring near the first tip and near the second tip.
 17. The cassette of claim 10, wherein the plurality of ridges are at least one of scalloped and serrated.
 18. A method of adjusting a position of a cam in a peristaltic pump, the method comprising: mounting a cassette to a peristaltic pump, the cassette comprising a cassette frame; a cam; a cam position selector switch; and a biasing member mounted to the cam and to the cassette frame and operably coupled with the cam position selector switch; moving the cam position selector switch in a first direction to release the cam position selector switch from the cassette frame; and moving the cam position selector switch in a second direction after releasing the cam position selector switch from the cassette frame to adjust a position of the cam relative to the cassette frame, wherein the second direction is approximately perpendicular to the first direction.
 19. The method of claim 17, wherein movement of the cam position selector switch in the second direction causes movement of the cam in the first direction.
 20. The method of claim 17, wherein the cam position selector switch comprises: a first edge, the first edge including a plurality of ridges; a second edge, the second edge generally opposite the first edge, the second edge inclined relative to the first edge; and a knob extending from the first edge. 